I usually take developers that talk about "balance" with a grain of salt. Pokemon has never been particularly well-balanced. The only thing they need to avoid is having something be a ruiner of worlds (ie Mewtwo and first gen). Is Dunsparce, Parasect or Purugly "balanced" in the game? Not really. With RPGs like this generally all the dev has to do is introduce a system that is suitably complicated, throw in a lot of variables and the player will create tier lists of their own.

So the going theory is that the addition to "bring balance to the force" adds a little bit of unbalancing so that something else needs to be added later on to rebalance it? Kinda like how we take meds for a condition then need to take other meds to counteract the side effects, thus making us chemically dependent on prescriptions?

Considering how addicted we are to Pokemon (and RPGs in general) I would buy this theory.

It's not hard to figure out, but every time they do something like that they kill a bunch of builds the same time they intend to introduce a lot of new ones.

EX: When they split physical and special Sceptile got its Leaf Blade build hit hard because it has high special attack.

It's probably worse in this case because the physical/special split was splitting into two different types whereas this time they're making two different properties split between 19 types, meaning moves can have up to 361 different combinations of properties. Combining with that that only a handful of moves are actually useful, the system would only add a lot of interesting aspects to gameplay if they plan on adding thousands of new attacks, which probably won't happen.

Though I guess the other option is to make said kinds of attacks very sparse so that they are only viable for special builds of Pokemon.